1. Technical Field of the Invention
The present invention relates to a motorcycle frame structure. More particularly, the present invention relates to a motorcycle frame structure including: a head pipe which pivotally supports a front fork and a steering handlebar connected to the front fork; a pair of left and right main frame sections extending rearward and downward from the head pipe; pivot plates continuously provided at rear portions of both the main frame sections so as to vertically and swingably support a front portion of a swing arm which rotatably supports a rear wheel at a rear portion thereof; and engine hangers provided integrally with both the respective main frame sections so as to extend downwardly from corresponding intermediate portions of the main frame sections.
2. Background Art
A conventional motorcycle body frame is known in which, to reduce the weight of main frame sections, the main frame sections are each provided with a through-hole above an engine hanger. A frame of this known design is described in Japanese Laid-open Patent No. 2000-72075.
Incidentally, as disclosed in Japanese Laid-open Patent No. 2000-72075, the main frame sections can be reduced in weight by provision of the through-holes. However, although weight-reduction can be promoted by increasing the size of the through-hole, it is necessary to prevent strength reduction resulting from the through-hole.
Although the known motorcycle frame has some utility for its intended purposes, a need still exists in the art for an improved motorcycle frame structure. In particular, there is a need for an improved motorcycle frame structure which allows for weight reduction of the main frame while preventing strength reduction.